This invention relates to an assembly and a method for fastening a stent onto a catheter. This kind of device finds routine use in the area of percutaneous transluminal coronary angioplasty (PTCA) procedures, although it may be used in other types of procedures, as well.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Inflation expandable stents are well known and widely available in a variety of designs and configurations. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with the crimping of inflation expandable stents although self-expanding stent may be used as well.
An example is the stent described in PCT Application NO. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
In advancing an inflation expandable balloon through a body vessel to the deployment site, the stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. Stents that are not properly secured or retained to the catheter may slip and either be lost or be deployed in the wrong location. The stent must be crimped in such a way as to minimize or prevent altogether distortion of the stent and to thereby prevent abrasion and/or reduce trauma of the vessel walls.
In the past, this crimping has been done by hand resulting in non-uniform crimps due to the application of uneven force to the stent. A non-uniformly crimped stent must either be discarded or re-crimped. Stents which have been crimped multiple times can suffer from fatigue. Moreover, a non-uniform crimping can result in scoring or other marking of the stent which can cause thrombosis. A poorly crimped stent can also damage the underlying balloon. Other methods of crimping stents include the use of mechanical devices such as those disclosed in U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085 to Timmermans et al., U.S. Pat. No. 5,626,604 to Cottone, Jr. and WO 97/20593.
It is a goal of the present invention to produce a device, optionally portable, to crimp a stent onto a catheter uniformly while minimizing the distortion of and scoring and marking of the stent and due to the crimping. This goal is accomplished in the present invention in its many embodiments by applying a uniform force to a compressible tube in which the stent and catheter are situated.
In the description that follows it is understood that the invention contemplates crimping a stent to a catheter with an expandable region. Thus, when reference is made to crimping a stent to a catheter, a balloon may be situated between the stent and the catheter,or the stent may be crimped to a region of a catheter having some other means for expanding.